1. Field of the Invention
The present invention relates to an improved system and method, using location defining data from global position satellites, to measure the precise distance between two objects on the surface of the earth. The invention is especially useful for accurately measuring the distance and direction between two objects on a golf course, such as the distance and direction between the hole or pin on a green associated with a fairway on a golf course and a golf cart located along the fairway, or the distance and direction between the hole or pin on a green associated with a fairway of the golf course or a hazard on the golf course and a golf ball on the fairway of the golf course, or the distance and direction between the club house of a golf course and a golf cart on the golf course.
2. Prior Art
For the sake of clarity, the term "hole" when used hereinafter shall refer to a combination of a teeing ground or tee, a fairway and a putting green associated with the fairway, on a golf course. It is well known in the field of golf, that a normal golf course consists of eighteen (18) holes; that each hole has a tee, a fairway and a green; and, that each green has a Hole or pin (hereinafter referred to as "pin") into which the golf ball is holed by a golf player (hereinafter referred to as "player"). These terms and their meaning, when used in reference to the game of golf are well known to persons knowledgeable in golf and it is in such context that these terms are used herein.
It is usual to inform a player the distance, in yardage, between the tee and the green for each hole on the golf course. However, in most cases, the pin on the green is moved from time to time and, for convenience of the golf club, the distance between the tee and the green is measured and given from approximately the geographical center of the teeing ground to approximately the geographical center of the green. This approximation is used despite the fact that the pin on the green is very seldom located at the geographical center of the green. Often, the distance between the tee and the green exceeds the distance a player drives the golf ball from the tee. When a player drives the golf ball short of the green, the player is left on his own to determine the distance or yardage between the golf ball on the fairway and the pin on the green of the hole being played.
The size, in area, of the green depends on the design of the golf course and, in many instances, the green may be a relatively large area. The pin, which is a hole in the green, not exceeding 108 mm in diameter and at least 100 mm in depth, (according to the 1996 Rules of Golf, published and copyrighted, 1995, by the United States Golf Association and The Royal and Ancient Golf Club of St. Andrews, Scotland) may be positioned anywhere on the green. The player, when addressing the green with his golf ball from the fairway, is most interested in knowing the distance, in yardage, as accurately as possible, between the golf ball on the fairway and the pin on the green associated with that fairway.
U.S. Pat. No. 4,815,020 to Cornier, issued Mar. 21, 1989 teaches that the distance between a golf ball and the green remaining after the tee-off flight of the golf ball, may be determined by measuring the distance of the flight of the golf ball from the tee and calculating the distance between the golf ball and the green, since the distance between the tee and the green is already known. The Cormier teaching provides for measuring the distance of the flight of the golf ball from the tee using dead reckoning, such as a wheel operated counter on a hand-drawn golf bag caddie cart, for example. The counter counts the revolutions of a wheel on the caddie cart as the caddie cart is pulled from the tee to the location of the golf ball on the fairway. This Cormier teaching leaves much to be desired. The basic measurement of distance used by Cormier is the distance from the center of the tee to the center of the green, not necessarily to the pin on the green. Cormier does not teach where, or how to find where, on the green, the pin is located. And, measuring distance by counting rotations of a wheel on a cart pulled across a rough terrain, is highly inaccurate because of the roughness of the terrain, slippage of the wheel and/or indirect routing of the cart.
U.S. Pat. No. 5,056,106 to Wang et al, issued Oct. 8, 1991 teaches that distances between a golf player and predetermined objects located on a golf course may be determined by using a plurality of radio transmitters positioned throughout the vicinity of the golf course. The radio transmitters, in predetermined locations, broadcast codified, spread-spectrum RF signals which are received by a hand-held receiver/processor which computes distances between the receiver and objects on the golf course. The teaching of Wang et al is overly complicated and expensive in equipment, installation and maintenance.
It is well known that the United States government has placed a plurality of global position satellites in orbit above the earth. The global position satellites (hereinafter referred to as "GPS") transmit RE carriers on which time and timing signal data are modulated. The GPS transmissions (hereinafter referred to as "GPS Data") may be received by a global position signal receiver (hereinafter referred to as "GPS receiver"). The GPS Data, received by a GPS receiver, may be translated or converted into location defining data, such as latitude and longitude coordinates, for example, that define an exact location, on earth, for the antenna of the GPS receiver receiving the GPS Data.
It is also known that the United States government has caused a contamination of the signals transmitted by the satellites in the global position indicating system. The contamination affects the GPS Data, causing a randomly occurring and changing inaccuracy in the location defined for the GPS receiver receiving GPS Data from satellites in the GPS system. The inaccuracy occurs and changes randomly, with time, in direction and in magnitude. Since the inaccuracy in the location defined for a GPS receiver receiving GPS Data is random in both occurrence and change, the location defined for a GPS receiver may be accurate or inaccurate, with respect to it actual location. Thus, although the GPS Data is correctly translated or converted, the location defined for the receiving GPS receiver may be accurate or inaccurate, the inaccuracy of the location defined being off-set from the actual, true location, in any direction, plus or minus, by as much as forty yards.
It is also known that the inaccuracy between the actual location of a GPS receiver and the location defined by the GPS Data received by the GPS receiver, can be corrected. Information relating to the global satellite location indicating system and the inaccuracy of the location data transmitted by the satellites and how to correct such inaccuracy, is reported in a paper, "The Application of NAVSTAR Differential GPS in the Civilian Community" by Jaques Beser and Bradford W. Parkinson, published in NAVIGATION, Vol.II, 1984.
U.S. Pat. No. 5,364,093 to Huston et al, issued Nov. 15, 1994 teaches that the distance between the pin on a green and a mobile cart may be determined using GPS Data transmitted from GPS when the exact location of the pin on the green and the exact location of the mobile golf cart are each known. The Huston et al teaching provides for previously determining the exact location of the pin on the green, by independent means. The mobile cart is provided with a GPS receiver and a computer. The GPS receiver receives GPS Data which, when translated, defines an inaccurate location for the mobile cart. A differential or error correction signal is used to change the inaccurate location of the golf cart to a correct location. The distance between the accurate location of the mobile golf cart and the previously determined location of the pin on the green is then calculated from two defined accurate locations.
The differential or error correction signal is generated by comparing position locating data derived from GPS Data received by a fixedly located GPS receiver with previously determined, corresponding position locating data defining the exact, correct location of the fixedly located GPS receiver. The differential signal is transmitted to the mobile GPS receiver on the golf cart. The exact location of the mobile cart is determined by correcting the GPS Data defining the inaccurate location of the mobile GPS receiver on the golf cart with the differential signal.
Huston et al, in their U.S. Pat. No. 5,364,093 patent teach measuring distance between a golf cart and the pin on the green. This leaves the player to measure the distance between the golf ball on the fairway and the pin on the green because golf carts are normally not permitted to trespass on the fairway of the golf course.
The U.S. Pat. No. 5,434,789 to Fraker et al, issued Jul. 18, 1995 teaches a golf diagnostic system which uses GPS Data for plotting locations for measuring the flight of a golf ball and for measuring distance between the GPS receiver and other previously known locations on the golf course. The teaching includes using differential or error correction signals generated by and transmitted from a fixed GPS receiver, located in a previously known and defined location, to adjust location coordinates, for accuracy. However, the teachings of both Huston et al, '093 and Fraker et al, '789 require the generation of differential or error correction signals. It is also necessary, in both teachings, to know the exact, defined location of at least one GPS receiver, in terms compatible with the GPS Data, in order to compare the GPS Data defined location with the actual location in order to generate a differential signal. The differential signal must be applied to a second GPS Data defining the location of a second GPS receiver in order to determine the correct location of the second GPS receiver. It is further necessary to know the exact, defined location of the pin in order to measure distance between the pin and a mobile GPS receiver.
The U.S. Pat. No. 5,438,518 to Bianco et al, issued Aug. 1, 1995 teaches that a digitized map of a golf course, stored in the memory of a computer, may be used to plot the location of a mobile unit on a golf course when GPS Data are received by the mobile unit. Raw GPS Data, defining an inaccurate location for the mobile unit, is corrected using a differential signal generated using location data translated from GPS Data and the previously known, correspondingly defined, actual location of a fixed GPS receiver. The location defined by the GPS Data, received by the fixed GPS receiver, is compared with corresponding data defining the known, exact location of the fixed GPS receiver and a differential signal is generated. The differential signal is transmitted to the mobile unit in order to correct the location of the mobile unit for position plotting.
The U.S. Pat. No. 5,469,175 to Boman, issued Nov. 21, 1995 teaches a system and method for accurately measuring the distance between a golf ball on a fairway and the pin on the green. The accurate location of a mobile golf cart carrying a GPS receiver is determined by correcting the inaccurate location derived from GPS Data received by the GPS receiver on the golf cart, using a differential or error correction signal The differential signal is generated by comparing GPS Data defining, inaccurately, the location of a fixed GPS receiver, with corresponding signal data defining the accurate location of the fixed GPS receiver. When the corrected location of the GPS receiver mounted on the golf cart is determined, the corrected location of the mobile GPS receiver is adjusted by the distance and direction between the golf ball on the fairway and the golf cart. This provides an accurate location of the golf ball on the fairway. The exact location of the pin is already known, and defined in corresponding location defining data and the distance between the golf ball on the fairway and the pin is calculated.
Each of the U.S. Pat. Nos. 5,364,093; 5,434,789; 5,438,518; and, 5,469,175 provides for correcting or changing GPS Data, with a differential or error correction signal, in order to convert an inaccurate location, derived from the GPS Data, to data that defines accurately a location for the GPS receiver. However, related differential or error correction data must first be determined and generated using GPS Data and the exact, previously defined location of a GPS receiver, which is defined in terms comparable with the GPS Data received from the global position satellites. After obtaining a corrected location of a mobile golf cart, distance between the golf cart and the pin is measured only when the exact location, of the pin is also previously known and defined in corresponding terms. These limitations are avoided by the present invention.
U.S. Pat. No. 4,949,089 to Ruszkowski, Jr. teaches a target locator system which uses the global position satellite system to provide location coordinates for a mobile target locator. The mobile target locator measures the distance, direction and inclination between the target and the mobile target locator. Location coordinates for the target are then generated by mathematically calculating the location coordinates for the target locator, obtained from the global position satellite system, with the measured distance, direction and inclination between the target locator and the target, providing a set of location coordinates for the target. The generated target location coordinates are transmitted to the weapons delivery system, which now has the location coordinates for the target.